Many types of nuts with positive locking are already known, the most common one is the castellated nut associated with a pin installed in a hole of the shaft on which the nut is screwed and which extends at one and the same time in this hole and in two crenels of the nut.
This particular type of nut has some disadvantages inherent to its structure, particularly an insufficient strength, a poor reaction to the vibrations and a limited effectiveness.
It has been improved by introducing a locking device in the nut with positive locking. This type of nut is particularly described in the documents FR-A-2 358 580 and U.S. Pat. No. 4,328,720.
Document EP-0 102 898 describes a particular example of a nut device with positive automatic locking intended to be fixed in rotation on the shaft and having a locking element.
In this document, the locking element has the shape of a threaded ring confined in a counterbore of the nut with which it is associated in rotation. The ring has serrations along its internal thread intended to cooperate with the complementary serrations of the threaded portion of the shaft when both threads of the ring and the nut are in phase.
Nevertheless, the effectiveness of such a nut may be compromised under the effect of vibrations.
Document FR-A-2 321 625 describes a lock nut comprising mainly a ring with internal serrations and an opened toric ring lodged in a circular groove located on the external part of this ring. One should note on the one hand that this ring is made in one piece, and on the other hand that this ring is in this case, acting as a retainer circular clip in the said nut to lock.
Document GB-A-547 624 mentions the possibility of a locking obtained by the pressure of the threads of the nut on those of the shaft, pressure obtained by a resilient toric opened ring pressing radially a rear and solidary skirt of the nut partially made malleable by radial millings. It will also be noted that the artificial segmentation obtained by millings in the nut is integrally making part of the nut. From another side, the obtained locking is a limited locking totally dependant of the friction capacities of the thread of the nut in relation to the thread of the screw.